Or just don’t worry about it unless you’re trying to band-aid a “dumb” converter that doesn’t know when enough is enough.
You could put a disconnect just downstream of the batteries or re-connect the converter on the downstream side of the existing disconnect.
I guess both of those options are fine if you don’t want to replace your existing converter with one that it won’t matter whether you leave the batteries hooked up. (If that’s even an issue, you didn’t say, but it’s the most plausible reason for your question. Imo.)